Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$104.38	7.462%	$112.1688	$112.17	$112.15	$112.20
Purchase #2	$128.43	11.631%	$143.3677	$143.37	$143.35	$143.40
Purchase #3	$108.87	3.377%	$112.5465	$112.55	$112.55	$112.50
Purchase #4	$72.26	9.216%	$78.9195	$78.92	$78.90	$78.90
Purchase #5	$39.48	7.113%	$42.2882	$42.29	$42.30	$42.30
Purchase #6	$195.78	13.748%	$222.6958	$222.70	$222.70	$222.70
Purchase #7	$56.29	5.792%	$59.5503	$59.55	$59.55	$59.60
7 purchase totals =	$705.49		$771.5368	$771.55	$771.50	$771.60